Instrument cluster Lights no worky on 65 Cuda

Hi guys, before I bore you with the whole story, perhaps someone can tell me if there exists a wiring diagram for a 65 Cuda. Perhaps in some original shop manual or later publication?

I searched this forum but my search powers are clearly broken as I couldn't find anything obvious.

My current dilemma is electrical gremlins. Nearly everything works, which is great, but I've got the following problems:

* Instrument lights are out
* Stock tachometer doesn't work

I've measured 12V across the fuse for the dash lights and see a corresponding drop when turning the rheostat on the head lamp switch so I believe this rules out the switch.

The little red lights between the two main gauges also work, so I don't believe it's a generic problem.

Does this old cuda have a printed circuit board for the instrument cluster?

At this point I realize a wiring diagram would go a long way or some basic advice.

Thanks!
Tom